1. Field of the Invention
This invention relates to a magnetic head for detecting changes in resistance of a magnetic thin film, the resistivity of which is changed with a recording magnetic field by a recording magnetic field from a magnetic recording medium, as a playback output voltage, and to a method for manufacturing the magnetic head.
2. Description of Related Art
Recently, a magneto-resistance effect device (MR device) has come to be used as a magneto-resistance magnetic head (MR head) in the field of a thin film magnetic head adapted for reproducing information signals recorded on, for example, a hard disc. The MR device, now in use, employs what is termed an anisotropic magneto-resistance device exhibiting a rate of change in resistivity of the order of 2%.
This MR head includes a MR device, the resistance of which is changed depending on the magnitude of the impressed magnetic field, and a bias conductor for applying the bias magnetic field across this MR device. For reproducing the information signals from a magneto-resistance effect by the MR head, the bias current is applied to the bias conductor for impressing the bias magnetic field across the MR device. Since the MR device has its resistance changed depending on the magnitude of the magnetic field from the magnetic recording medium, the information signals recorded on the magnetic recording medium can be reproduced based on changes in the voltage value caused by changes in resistance.
If, in this MR head, the MR device is arranged relative to the magnetic recording medium so that the reproducing current will be caused to flow perpendicularly relative to the magnetic recording medium, the magnetic recording medium can be reduced in track width to enable the information signals to be reproduced.
For improving the recording density of the magnetic recording medium, such as a hard disc, there are known a method of narrowing the track width for increasing the track density and a method of increasing the line recording density.
For increasing the line recording density, there is known a method of narrowing the magnetic gap provided on a recording magnetic head for generating a steep recording magnetic field by the magnetic gap for recording information signals and reproducing the information signals recorded by this recording magnetic head by a MR head with high resolution.
On the other hand, for increasing the track density, there is known a method of decreasing the track width of the magnetic head during recording and/or reproduction. At this time, a MR head of high playback output is indispensable for not lowering the playback output of the recorded information signals.
Meanwhile, in the above-described MR head, the longitudinal size of the MR device along the track width needs to be precisely set in manufacturing the MR device in keeping up with the decreasing track width brought about by the recent demand towards higher recording density. In a compound magnetic head, in which the above-mentioned MR head is unified with an induction type recording magnetic head, it is necessary to set the relative position of the MR device and the magnetic core within a pre-set offset range in manufacturing the MR head. Therefore, the allowance of the relative positions of the MR device and the magnetic core in the manufacturing process for the compound magnetic head is extremely small.
However, with the above-described compound magnetic head, made up of plural thin films layered together with a thickness of each layer being several micrometers, it is not that easy to observe the offset value within an allowable range. Moreover, with the above-described compound magnetic head, since the longitudinal size along the track width of the magnetic gap by the MR device and the magnetic core is diminished in keeping up with the demand for reduction in track width of the magnetic recording medium, magnetic influences ascribable to the shape of the terminal end of the MR device and the magnetic core become predominant. Thus, with the present MR device and the magnetic core, it is not that easy to diminish the longitudinal size thereof in the track width direction.
Thus, the MR head suffers from the problem that, in the manufacturing process of the MR head, the production yields are lowered due to the error exceeding the above-mentioned allowable range of the offset value and to the error in the longitudinal size of the magnetic gap along the track width.